1. Field of the Invention
The invention relates to a rotating disc diluter for fluid flows, with a rotatable rotary element which has surface-accessible discrete transfer volumes which along their common path of movement alternately glide over feed and discharge ports for the undiluted fluid flow on the one hand and for a dilution fluid flow on the other hand.
2. The Prior Art
Such arrangements, which are also referred to as carrousel diluters, for example are known from “Journal of Aerosol Science, 1997, Vol. 28, Nr. 6, pages 1049 to 1055” and are mostly used for taking measurements of liquid or gaseous fluid flows and especially when for the better utilization of limited measuring ranges of the measuring devices defined pre-dilutions are required in a dilution rate range which is as large as possible. A basic block of the arrangement which is known from the mentioned literature reference has two connecting passages; one for the undiluted fluid flow (an aerosol-laden gas in that case), and the other for an aerosol-free dilution fluid flow. The two passages have feed and discharge ports on the same outside surface of the basic block and are covered by the rotary element which is driven via a stepper motor and which for reducing the friction consists of synthetic material with corresponding admixtures. The transfer volumes, which are arranged in the rotary element on the side facing the feed and discharge ports, glide over the ports during the rotation of the rotary element and as a result are filled with a controllable portion of the aerosol-laden fluid flow which at the corresponding ports for the dilution fluid flow is then carried along again by this. The dilution ratio is therefore a function of number and volume of the discrete transfer volumes as well as of the dilution fluid volumetric flow and of the rotational speed of the rotary element.
In a constructionally somewhat differently constructed arrangement of the type which is mentioned in the introduction, instead of a rotary element which is provided on one side with cavities, a perforated disc is provided, the continuous transfer volumes of which are filled or emptied in the throughflow direction from the feed port to the discharge port. The supplied aerosol-laden fluid flow is completely freed of the aerosol downstream of the rotary element in a filter and then as a dilution fluid flow is fed to the other side of the rotary element. If the rotary element is stationary, no aerosol-laden partial volume is tapped off and fed on the other side, so that no aerosol remains in the fluid flow which is fed to the measuring device. If the rotary element is rotated, a certain portion of the aerosol-laden fluid flow is again added to the particle-free dilution fluid flow, with which the dilution rate in turn is variable across the same parameters as referred to above.
In the case of the known arrangements of the type mentioned in the introduction, it is disadvantageous that the adjustable dilution rate range is relatively tightly limited and can be shifted up or down only by means of constructional alterations to the interacting elements, but even then can hardly be widened.
It is the object of the present invention to improve a rotating disc diluter of the type mentioned in the introduction so that the mentioned disadvantages of the known arrangements are avoided and so that in a simple manner a significant increase of the usable dilution rate range especially becomes possible.